/*
 *  Copyright 2008-2011 NVIDIA Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#include <thrust/iterator/iterator_traits.h>

#include <thrust/detail/backend/dereference.h>
#include <thrust/detail/backend/cpp/detail/copy_backward.h>

namespace thrust
{
namespace detail
{
namespace backend
{
namespace cpp
{
namespace detail
{

template <typename RandomAccessIterator,
          typename StrictWeakOrdering>
void insertion_sort(RandomAccessIterator first,
                    RandomAccessIterator last,
                    StrictWeakOrdering comp)
{
  typedef typename thrust::iterator_value<RandomAccessIterator>::type value_type;

  if (first == last) return;

  for(RandomAccessIterator i = first + 1; i != last; ++i)
  {
    value_type tmp = backend::dereference(i);

    if (comp(tmp, backend::dereference(first)))
    {
      // tmp is the smallest value encountered so far
      thrust::detail::backend::cpp::detail::copy_backward(first, i, i + 1);
      backend::dereference(first) = tmp;
    }
    else
    {
      // tmp is not the smallest value, can avoid checking for j == first
      RandomAccessIterator j = i;
      RandomAccessIterator k = i - 1;

      while(comp(tmp, backend::dereference(k)))
      {
        backend::dereference(j) = backend::dereference(k);
        j = k;
        --k;
      }

      backend::dereference(j) = tmp;
    }
  }
}

template <typename RandomAccessIterator1,
          typename RandomAccessIterator2,
          typename StrictWeakOrdering>
void insertion_sort_by_key(RandomAccessIterator1 first1,
                           RandomAccessIterator1 last1,
                           RandomAccessIterator2 first2,
                           StrictWeakOrdering comp)
{
  typedef typename thrust::iterator_value<RandomAccessIterator1>::type value_type1;
  typedef typename thrust::iterator_value<RandomAccessIterator2>::type value_type2;

  if (first1 == last1) return;

  RandomAccessIterator1 i1 = first1 + 1;
  RandomAccessIterator2 i2 = first2 + 1;

  for(; i1 != last1; ++i1, ++i2)
  {
    value_type1 tmp1 = backend::dereference(i1);
    value_type2 tmp2 = backend::dereference(i2);

    if (comp(tmp1, backend::dereference(first1)))
    {
      // tmp is the smallest value encountered so far
      thrust::detail::backend::cpp::detail::copy_backward(first1, i1, i1 + 1);
      thrust::detail::backend::cpp::detail::copy_backward(first2, i2, i2 + 1);
      backend::dereference(first1) = tmp1;
      backend::dereference(first2) = tmp2;
    }
    else
    {
      // tmp is not the smallest value, can avoid checking for j == first
      RandomAccessIterator1 j1 = i1;
      RandomAccessIterator1 k1 = i1 - 1;

      RandomAccessIterator2 j2 = i2;
      RandomAccessIterator2 k2 = i2 - 1;

      while(comp(tmp1, backend::dereference(k1)))
      {
        backend::dereference(j1) = backend::dereference(k1);
        backend::dereference(j2) = backend::dereference(k2);

        j1 = k1;
        j2 = k2;

        --k1;
        --k2;
      }

      backend::dereference(j1) = tmp1;
      backend::dereference(j2) = tmp2;
    }
  }
}

} // end namespace detail
} // end namespace cpp
} // end namespace backend
} // end namespace detail
} // end namespace thrust

